There are a wide variety of chemicals in such cleaners ranging from what I suspect is little more than mineral spirits to some pretty strong things. Some additionally have a chemical (methanol is popular) that grabs hold of water in the fuel and carries it along to the engine in a form that won't get into trouble.
I'm not sure what the difference is between fuel-injector and carburetor cleaner, especially at typical dilutions of a pint or less in 10-20 gallons of gas.
I put in a can of B-12 Chemtool, one of the more vigorous ones and also not terribly expensive, a couple of times a year -- after an extended period of commuting unrelieved by highway travel, or if engine performance degrades suddenly upon refueling (indicating bad gas). That's also the brand of spray carb cleaner that I use.
Excessive use of the stronger kinds is said by some to entail a risk of leaving deposits on your plug insulators. Also, hold a rag at the ready so they don't get on your paint.
Of course, these additives will only serve to take things *off* fuel injectors, not build them up. If the problem is a worn or damaged injector, it'll still be a worn or damaged injector, just cleaner -- a change that might help some but won't make it like new again.
Note that these days most name-brand gas has some kind of additives in it to keep things cleaner, modern computer-controlled cars are less likely to go into an over-rich condition (though if the engine is worn, oil fouling is still possible), and modern ignitions are much more able to blast through a slightly fouled plug.
If your desire for a cleaner is triggered by some dubious gas, consider changing your fuel filter(s) after exorcising the stuff, too.
Cheers,
--Joe